There he is!where have you been hiding Pete?Good to see you around,we have been needing some profession help around here .Answering by request... it is definitely a Confederate Read Long-Model shell. Although it resembles a yankee Parrott shell, its iron body and the copper "ring sabot" on its base were designed by Dr. John B. Read of Tuscaloosa Alabama. Also, your find has a Confederate copper fuzeplug in its nose.
Although your Read shell's copper ring-sabot is bent at one spot, the rest of it looks unfired. Please post some additional closeup photos of the sabot so I can tell for sure whether it is unfired or not. If it is an unfired one, there might be more of them in the ground nearby.
Since you are digging in the Marietta/Atlanta GA area, call Carl Sitherwood, a close friend of mine who is a long-experienced Professionally at safely remove the powder-charge from civil war era artillery shells. Tell him I sent you. You can contact him as CarlS at bulletandshell.com.